Document observer status

site/ipam/troubleshooting-ipam.md

@@ -31,7 +31,9 @@ the total allocation range and default subnet. Columns are as follows:
     * 'awaiting consensus' - an attempt to achieve consensus is
       ongoing, triggered by an allocation or claim request;
       allocations will block.  This state persists until a quorum of
-      peers are able to communicate amongst themselves successfully
+      peers are able to communicate amongst themselves successfully.
+      The Status may also show '(observer)' instead of the quorum size,
+      if this peer has been started with the `--observer` option.
     * 'ready' - consensus achieved; allocations proceed normally
     * 'waiting for IP range grant from peers' - peer has exhausted its
       agreed portion of the range and is waiting to be granted some